Regarding carbon nanotubes (CNTs) that are expected for development to functional materials as novel electronic device materials, optical materials, electrically conductive materials, biotechnology-related materials and others, energetic investigations of their yield, quality, use, mass productivity and production method are being promoted.
For putting carbon nanotubes into practical use for the above-mentioned functional materials, one method may be taken into consideration, which comprises preparing a bulk aggregate of a large number of carbon nanotubes, large-scaling the size of the bulk aggregate, and improving its properties such as the purity, the specific surface area, the electric conductivity, the density and the hardness to thereby make it patternable in a desired shape. In addition, the mass productivity of carbon nanotubes must be increased greatly.
To solve the above-mentioned problems, the inventors of this application have assiduously studied and, as a result, have found that, in a process of chemical vapor deposition (CVD) where carbon nanotubes are grown in the presence of a metal catalyst, when a very small amount of water vapor is added to the reaction atmosphere, then an aligned carbon nanotube bulk aggregate having a high purity and having extremely large-scaled as compared with that in conventional methods can be obtained, and have reported it in Non-Patent Document 1, etc.    Non-Patent Document 1: Kenji Hata et al., Water-Assisted Highly Efficient Synthesis of Impurity-Free Single-Walled Carbon Nanotubes, SCIENCE, 2004.11.19, Vol. 306, pp. 1362-1364.